Device for superfinishing machined surfaces



12, 1952 c. A. L."THERY DEVICE FOR SUPERFINISHING MACHINED SURFACES Filed Nov. 50, 1949 j 3 Sheets-Sheet 1 Ian/aural? Aug. 12, 1952 c. A. L. THEIRY 2,606,410

DEVICE FOR SUPERFINISHING MACHINED SURFACES Filed Nov. 50, 1949 v s, Sheets-Sheet 2 uran aaqigm @wwM M Aug. 12, 1952 c. A. L. THERY DEVICE FOR SUPERFINISHING MACHINED SURFACES Filed Nov. 30. 1949 3 Sheets-Sheet 5 Patented Aug. 12, 1952 DEVICE FOR SUPERFINISHING MACHINED SURFACES Constant A. L. Thry, Paris, France, assignor to Y Societe Nationale dEtucle et de Construction de Moteurs dAviation, Paris, France, a company of France Application November 30, 1949, Serial No. 130,093

In France December 14, 1948 2 Claims. 1

Modern investigation methods of surface conditions of machined members have revealed the relatively rough character of surfaces which had undergone machining operations and were considered up to then as finished. This has led to the technique nowadays known as superfinishing and enabling to achieve a. far more elaborate finish of these machined surfaces owing to the application of very fine abradants under relatively moderate pressures.

Tests performed on engines have proved that the premature wear of certain members was due to the bad surface condition of rubbing and rotating parts and that, from this standpoint, superfinishing leads to a definite advantage.

Implements recently manufactured for performing this operation constitute heavy, complex and expensive machine-tools. Besides, in these implements, the abrasive stone used for superfinishing is applied on the treated member owing to the pressure of torsional coil springs arranged normally to the surface to be superfinished. This arrangement renders certain operations diflicult or impossible; this is the case in particular of the superfinishing of the inner surface of a boring.

The present invention has for its object a superfinishing appliance for improving surface conditions wherein an abrasive stone or grinding mill is mounted on a spring leaf which constitutes both the material support of said stone and the pressure generating member, said spring being preferably secured to a slide liable to effect a reciprocating motion which equalizes the slight wear caused by the stone to the treated surface. By this means, it is possible to give to the stone mounted on its resilient support any desired direction and to superfinish both outer and inner surfaces, thus obtaining a superfinishing tool of universal character.

According to a further improvement which is also an object of the invention, and which is aimed at obtaining a reciprocating motion of the stone, an air-turbine of the type driving rotating abrasive rods or small grinding wheels is used, this avoiding to resort to a direct current'varying rate electric motor requiring a current rectifier for its feeding by ordinary alternating means. The rotating motion of the air-engine whose rate may easily be adjusted by throttling more or less the intake, is converted into a reciprocating motion of the slide to which the leaf spring carrying the stone through an adjustable eccentric gear, is secured, thus enabling to vary at will the amplitude of the oscillations of the stone.

The slide may be provided, on various sides,

with means for securing the leaf spring carrying the stone, so as to allow, in every practical case, the easiest arrangement and direction setting of that spring.

The previous dispositions may be effected on a machine comprising its own bed and its means for securing, centering and driving the superfinishing stone, but they also enable to constitute with the leaf spring carrying the stone, the engine and the converter of rotation motion into reciprocating motion,'all fixed on a small bed, a complete cheap superfinishing unit of small bulkiness liable to be mounted on any machinetool, and on which the securing and driving means of the member to be superfinished, are located.

To this respect, the invention gives machiners disposing of machine-tools such as lathes, particularly handy, simple and cheap means for superfinishing all kinds of members.

Other objects and advantages of the invention will be apparent during the course of the following description.

In the accompanying drawing forming a part of this application and in which like numerals are employed to designate like parts throughout the same:

Fig. l is a perspective view of a superfinishing tool according to the invention, this tool being shown in the position corresponding to the superfinishing of a cylindrical outer surface,

Fig. 2 is an elevation and vertical section view of this tool, on a larger scale,

Fig. 3 is a partial section of the slide and its guide along line IIIIII of Fig. 2, line IIII of Fig. 3 representing the trace of the sectional plane of Fig. 2,

Fig. 4 is a projection and horizontal section view of the tool,

Fig. 5 is a view as seen from beneath, of the plate converting rectilinear motion into reciprocating motion,

Figs. 6, 7 and 8 are partial perspective views similar to Fig. 1 representing various arrangements of the leaf spring carrying the stone for superfinishing respectively an inner cylindrical surface (of a boring), a plane surface, and teeth of a spur gear, and

Fig. 9 is a diagrammatic view of a small centerless type machine.

The superfinishing tool shown in the drawings comprises a bed I made of a thick usually vertical sheet occasionally ribbed in order to stiifen it, this bed being provided at its basis with an appendage 2 made of thick iron and designed to be tightened, for instance, between the jaws 3 of the carriage of a lathe (Fig. 2). Sheet I is secured to the appendage 2 preferably by means of a bolt 4 whose head 4a may be adjusted inside a T-groove located in appendage 2, tightening being effected by means of a nut 6, on the flange I of an angle-iron. The other flange 8 of the angle-iron is secured to sheet I by means of bolts 9 crossing elongated holes III allowing for a certain height adjustment of sheet I. In the medium part of this sheet a U-shaped grooved bar II with horizontal flanges is secured. Inside this bar, a slide may move parallel to the plane of sheet I; one of the ends of a leaf spring I2 is secured to this slide, the opposite free end carrying the superfinishing abrasive stone I3. The slide is made of two portions (see also Fig. 3) viz. on the one hand snug I4 guided inside groove II and held therein by means of four sets of balls I5 arranged in V-shaped slots I6 in the groove and the snug, and on the other hand a head I! secured to snug I4 by means of dowels I8 and nuts I9. At the ends of the groove, the balls are prevented from falling off by means of small plates ISa secured both to the groove and to the snug I4, the maximum displacement of the snug inside the groove being thus equal to the total clearance between the balls. Snug I4 is secured, by means of screws to a rod 2| engaged in a hole of this snug and liable to slide freely at its opposite end inside a small bushing 22 of a flange 23. This flange is secured to a base-plate 24 integral with the fixed portion II of the grooved bar. In its medium portion, rod 2| carries a transverse slot or groove 25 (see also Figs. 4 and 5) into which is engaged a finger 26 carried by a slide 21. This slide is secured in an adjustable way in a diametral slot 28 of a plate 29. The axle 3B of this plate is fast in rotation with the shaft end 3| of a turbine air-engine 32, clamped by means of collars 33 to the upper part of sheet I. (In the drawing, this engine whose intake is in 34 and whose intake adjustment ring is in 35, is of a commonly used type for driving small grinding mills or abrasive rods.) The whole arrangement formed by the plate 29 designed to be rotatively driven more or less rapidly by the engine 32, by the slide-block 21 and by its finger 26, constitutes an eccentric gear whose offsetting is adjustable between 0 and a few millimetres. The adjustment of the offsetting being carried out by unscrewing both screws 36 holding fast the slide 21 in the diametral groove 28 of plate 29, by displacing them through the desired distance, the slide 21 inside said groove, then by screwing again screws 36, the displacement of the slide being made possible owing to the fact that the screws 36 cross stud-holes 31 of this slide; an indicator 38 carved on the slide and cooperating with a scale 39 carved on the plate (or inversely) enables to read the value of the offsetting obtained by finger 26. When this oifsetting is non-existent, the rotation of the shaft 3| of the air-engine and of plate 29 does not obviously transmit any movement to rod 2| and to slide I4, I! connected to the stone carrying spring I2. When this offsetting has a certain value, finger 26 describes a circle around the axis of shaft 3| and in cooperating with the groove 25 of rod 2|, it transmits to this rod a reciprocating translation motion whose value depends on the offcentering of finger 26. This reciprocating translation is imparted by rod 2| to the slide I4, I! which moves on balls I5 and finally to the stone I3 through spring I2.

The head I1 is provided with one or more slots having a T cross-section such as 40 into which it is possible to engage slidably the head of a bolt 4| used for securing to this head the end of the leaf spring I2 which is then tightened by means of a nut 42. This arrangement allows various direction setting of the leaf spring I2 and of the stone, as seen by comparing for instance with one another Figs. 1 and 6.

The base plate 2 of bed I which carries all the members, being tightened on the carriage of a machine-tool, for instance of a lathe, which may take, as known, two translation motions, one parallel to the main axis of the machinetool, the other transversal, it is possible to move the device and the stone I3 near any circular surface centred on the machine-tool and driven by it.

In the embodiment shown in Fig. 1, the surface to be superfinished is one of the outer cylindrical surfaces 43 of a member 44. The latter is secured to and centred on the headstock of the lathe which rotatively drives it. When operating the carriage of the lathe, the stone I3 is brought upon surface 43 and the pressure of this stone on said surface is adjusted at will, this pressure corresponding to a certain resilient fiexion of the leaf spring I2. The position of the slide 21 will have previously been adjusted on plate 29, so as to have the desired amplitude for the oscillations of the stone I3 which will take place parallel to the generatrices of the cylindrical surface 43 to be superfinished. The stone I3 being in contact with the surface 43, the lathe v is started in order to rotate this surface about its axis on the one hand, and the air-engine 32 in order to cause oscillations of stone I3 on the other hand. As superfinishing proceeds, the carriage is displaced parallel to the axis of rotation of member 44, i. e. to the generatrices of surface 40.

In the example of Fig. 6, it is proposed to superfinish the inner surface of a boring 45 of member 44, the spring leaf I2 carrying the stone is then arranged parallel to the axis of member 44, this allowing the fixing of this leaf on head II.

In the example of Fig. '7, the device is applied to the superfinishing of a plane surface 46 perpendicular to the rotation axis of member 44. The base plate 2 of bed I is then arranged on the carriage of the lathe so that the bed I be perpendicular to the rotation axis.

The example of Fig. 8 only differs from that of Fig. 1 in so far as the stone I3 is replaced by a regrinder I3a in the shape of a gear for regrinding the teeth of a gear 41 which is rotatively driven about its axis by the lathe.

Lastly, Fig. 9 shows a device designed for superfinishing small members such as rollers. In the shown example, the spring leaf I2 is in a horizontal plane so that stone I3 is applied on the top of the roller 48 to be superfinished. The spring leaf I2 is then secured in the groove 48a which is seen in Figs. 1 to 8 underneath the sliding head II. The roller to be superfinished 43 is applied by its weight and by the pressure of stone I3 on two rollers 49, 50. It is further rotatively driven by at least one of these rollers 43 whose axle is made fast with the headstock of the lathe, the other roller 50 being loose or not. The axle of roller 50 revolves in a bed 5| which may be designed so as to facilitate setting in position the rollers to be superfinished and their ejection after treatment. For this purpose, this bed 5| carrying the axle of roller 5!] is hinged about the axle of roller 49, so that by pivoting this bed 5| about said axle, the roller 50 is moved further from or nearer to the roller 48 to be superfinished. The bed 5| is held in position during the superfinishing operation by means of a crutch 52 which may be resilient. This crutch is hinged in 53 upon bed 5| and takes support through its inner end 54 on the bed 55 of the lathe. In Fig. 9 the members are in operating position. The pressure exerted by the spring leaf I2 together with the reaction of the resilient crutch 52 keep between stone 3 and rol1er48 the friction required for superfinishing, while stone l3 receives from the air-engine its oscillation parallel to the generatrices of the roller, i. e. perpendicularly to the plane of Fig. 4. When the superfinishing operation of roller 48 is completed, crutch 52 is moved away from its support point 55 by pivoting it about hinge 53. Bed 5| is then lowered by pivoting about the axis of roller 49. A finger 56, pivotally mounted in 5'! on bed 5| and held in its position by a counterweight 58, comes and meets roller 48 which has gone down while remaining in contact with both rollers 49 and 50. Owing to the angular velocity it has reached, roller 48 resting upon the end of finger 56, is hurled on an incline 59 integral with the bed 5| and is automatically ejected by rolling over this incline. With this same incline, it is possible to introduce a new roller, then the members are immediately put back in operating position by means of crutch 52.

It is to be understood that the form of the invention herewith shown and described is to be taken as a preferred example of the same and that various changes in the shape, size and arrangement of parts may be resorted to without departing from the spirit of the invention or the scope of the subjoined claims.

What I claim is:

1. A device for superfinishing machined surfaces comprising, in combination, a rotary pneumatic engine, an eccentric gear drivingly connected to said engine, means on said eccentric gear for adjusting the eccentricity thereof, a slide mounted for reciprocating motion and driven from said eccentric gear, a resilient arm associated at one end thereof with said slide and generally extending in the reciprocation plane of said slide, means for adjusting the angular setting of said arm relatively to said slide in the reciprocation plane thereof. and an abrasive member carried by said arm at the other end thereof.

2. A device according to claim 1 wherein the means for adjusting the angular setting of the arm relatively to the slide, includes a bolt crossing a hole through said arm and constituting a pivot for said arm, and a nut screwed on said bolt and adapted to tighten said arm on said slide, whereby the angular setting of said arm relatively to said slide can be adjusted between 0 and 360 in the reciprocation plane.

CONSTANT A. L. THERY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 818,167 Hatfield Apr. 17, 1906 1,270,808 Franklin July 2, 1918 2,195,066. Wallace Mar. 26, 1940 2,244,806 Schmidt June 10, 1941 2,257,452 Binns et a1 Sept. 30, 1941 2,354,347 Peets July 25, 1944 2,479,112 Hegeman Aug. 16, 1949 

